1. Field of the Invention
The present invention relates to a movable-body apparatus with a movable body which can be reciprocally tilted about a twisting longitudinal axis, such as micro-actuators, and an optical deflector using an electromagnetic actuator, an optical instrument using the optical deflector, and a method of fabricating the movable-body apparatus.
2. Description of the Related Background Art
An optical deflector for defecting and scanning a light beam, such as a laser beam, is used in an optical instrument, such as a laser printer and a bar-code reader. As the optical deflector, there exist a polygonal mirror in which a polygon with side mirrors is rotated to reflect and deflect a light beam incident thereon, and a galvano-mirror in which a flat mirror is vibrated by an electromagnetic actuator.
However, an electromagnetic motor for rotating the mirror is needed in the polygonal mirror, and a driver coil formed by mechanical winding and a large-sized yoke for generating the magnetic field are needed in the galvano-mirror. Therefore, there exists the limitation to a decrease in the size of the mechanical elements mainly due to required output torque. Further, the size of an optical deflecting apparatus inevitably increases due to a required space in which component members are assembled.
Furthermore, where a light beam is scanned in a two-dimensional manner, a combination of the polygonal mirror and the galvano-mirror, or a combination of two polygonal mirrors is generally employed. However, when an accurate two-dimensional scanning should be attained, it is necessary to arrange the mirrors such that scanning directions are orthogonal to each other, and hence, their optical adjustment is very complicated.
Apparatuses disclosed in Japanese Patent Application Laid-Open Nos. 7(1995)-175005 and 7(1995)-181414 are known as optical deflectors proposed to solve the above-described disadvantages. In those apparatuses, semiconductor producing techniques are applied and micromachining techniques for integrally fabricating micro-machines on semiconductor substrates are used.
FIG. 1 illustrates an example disclosed in Japanese Patent Application Laid-Open No. 7(1995)-175005. In a galvano-mirror 1001 of FIG. 1, a planar movable plate 1005 with a light reflective mirror 1008 is rotatably supported relative to a silicon substrate 1002 by a pair of torsion springs 1006 formed of a monolithic silicon. There are further arranged an upper-side glass 1003, a lower-side glass 1004, a flat coil 1007, contact pads 1009, and permanent magnets 1010A, 1011A, 1010B and 1010C. In this structure, the driver coil 1007 for generating the magnetic field is disposed on the periphery of the movable plate 1005, and paired permanent magnets 1010A and 1010B; 1011A and 1010C are disposed on upper and lower surfaces of the semiconductor substrate 1002, respectively, through upper and lower glass substrates 1003 and 1004, such that electrostatic fields are applied only to portions of the flat coil 1007 parallel to the twisting longitudinal axis of the torsion springs 1006.
In this optical deflector, when a current is caused to flow through the flat coil 1007, the Lorentz force appears in a direction determined by the Fleming""s left-hand rule due to the current flowing through the flat coil 1007 and the magnetic flux generated by the magnets 1010A and 1010B; 1011A and 1010C. Thus, a moment for rotating the movable plate 1005 occurs. Upon rotation of the movable plate 1005, a spring reaction force occurs due to the spring rigidity of the torsion springs 1006. A static displacement of the movable plate 1005 is established based on an equilibrium relationship between the Lorentz force and the spring reaction force. When an alternate current is caused to continuously flow in the flat coil 1007, the movable plate 1005 with the reflective mirror 1008 is reciprocally tilted in a vibratory manner, and a light beam reflected by the mirror 1008 is hence scanned.
The optical deflector of FIG. 1, however, has the following disadvantage. When a vibratory angle of the light beam is to be increased at the scanning time, distances between the upper and lower glass substrates 1003 and 1004 and the movable plate 1005 must be enlarged. Then, distances between the permanent magnets 1010A and 1010B; 1011A and 1010C and the flat coil 1007 increase, and hence, the magnetic flux by the permanent magnet weakens at the location of the flat coil 1007. As a result, a large current is required to flow through the flat coil 1007 for the driving of the movable plate 1005, and it hence becomes difficult to construct an optical deflector which can achieve a large deflection angle and reduce a consumption electric power. Further, since the permanent magnets 1010A and 1010B; 1011A and 1010C for generating the external magnetic field must be disposed outside the movable plate 1005, an external size of the entire device inevitably increases. The movable plate 1005 provided with the flat coil 1007 also increases in size.
Further, in the deflector of FIG. 1, the wiring of the flat coil 1007 for driving the movable plate 1005 is formed on the torsion springs 1006. Accordingly, there is a possibility that a metal material of the wiring is damaged and disconnected due to the repetitive torsional motion of the torsion springs 1006 at the time of driving the movable plate 1005. Such disconnection of the wiring greatly limits the life of the device.
FIG. 2 illustrates an example disclosed in Japanese Patent Application Laid-Open No. 7(1995)-181414. In a structure of FIG. 2, a minute driving source 2006 for generating a minute vibration of a piezoelectric oscillator is provided at an end of an elastic support 2003 which has two elastic deformation modes of bending mode xcex8B and torsion deformation mode xcex8T. The other end of the elastic support 2003 is shaped into an oscillator 2002 with a light reflective surface 2007. In this structure, there are further arranged a vibration input portion 2004, a mirror support 2008, and a plate 2009.
In the optical deflector of FIG. 2, flexure vibration and torsional vibration of the elastic support 2003 are caused by the vibration from the driving source 2006. Since there are characteristic resonance vibration modes of the flexure vibration and the torsional vibration in accord with the construction of the device, the elastic support 2003 resonates at the resonance frequency when the vibration source 2006 generates a vibration including frequency components of those two resonance frequencies. Thus, the oscillator 2002 with the reflective surface 2007 can scan a reflected light beam in a two-dimensional manner.
In the optical deflector of FIG. 2, however, scanning rate and waveform of the oscillated light beam are limited since the driving and optical scanning cannot be achieved at frequencies other than the resonance frequency. Further, the driving manner, in which the attitude of the reflective surface 2007 is maintained, cannot be performed.
Furthermore, in the optical deflector of FIG. 2, the elastic support 2003 is oscillated in two deformation modes of bending mode and torsion mode. Therefore, in the case of a two-dimensional scanning, a resultant force of bending stress and shear stress appears, and a large internal stress is hence generated in the elastic support 2003, in contrast to the case of a single stress. As a result, the elastic support 2003 is easy to break, and the life of the device is greatly limited.
In addition to the above, the fabrication of an electromagnetic actuator on a substrate, such as silicon, has been recently tried by using semiconductor processes. When the electromagnetic actuator is fabricated using the semiconductor process, a unit of a stationary core, a moving core and an electromagnetic coil can be integrally fabricated. Accordingly, no joining and bonding processes is needed, and those elements can be aligned with a high precision. Further, mass-production is possible, and the cost can hence be decreased.
Japanese Patent Application Laid-Open No. 2000-235152 discloses an example in which the electromagnetic actuator formed on a substrate is applied to an optical deflector. FIG. 3 illustrates the optical deflector disclosed in this Japanese reference. This is directed to a torsion beam optical deflector, and used as a deflector for two-dimensionally scanning a laser beam. The deflector includes an inner y-axis-directional deflector 3003, an outer x-axis-directional deflector 3004 and an outermost frame 3001. The inner y-axis-directional deflector 3003 includes a substrate with grooves 3002, a movable plate 3006 rotatably supported by axis portions 3005 and having a hard magnetic thin layer on its surface, a pair of thin electromagnet portions 3007 for rotatably driving the movable plate 3006, and a mirror 3008 provided on the movable plate 3006. Formation planes of the movable plate 3006 and the thin electromagnets 3007 are slightly shifted from each other in a thickness direction.
The movable plate 3006 is oscillated by Coulomb forces appearing between magnetic fields generated by an alternate current at 60 kHz, which is the structural resonance frequency of the y-axis-directional deflector 3003, flowing in the electromagnet portions 3007 and by the hard magnetic thin layer on the movable plate 3006. Light incident on the mirror 3008 is thus deflected. Consumption electric power can be reduced due to a driving method using the mechanical resonance. The outer x-axis-directional deflector 3004 has the same structure as that of the inner y-axis-directional deflector 3003, and also is driven similarly. Driving frequencies are 60 kHz (y-direction) and 60 Hz (x-direction), and the displacement angle is xc2x113.6xc2x0 (y-direction).
In the optical deflector of FIG. 3, however, the cross-sectional area of a core of the electromagnet 3007 is limited in size since this core is composed of a thin layer deposited by sputtering, though a high speed operation can be obtained. Therefore, the magnetic flux is inevitably saturated when a large current is caused to flow in the thin electromagnet portion 3007, and it is hence difficult to further increase the displacement angle. Further, the shift between the formation planes of the movable plate 3006 and the thin electromagnet portions 3007 in the thickness direction is small, so a further increase in the displacement angle is limited also for this reason.
It is an object of the present invention to provide a movable-body apparatus with a movable body which can be reciprocally tilted about a twisting longitudinal axis, such as micro-sensors for sensing mechanical amounts, micro-actuators, and optical micro-deflectors, which can be reduced in size and cost, and have an excel lent durability and a versatile performance, and in which a large tilt displacement of the movable body is possible, an energy efficiency can be increased, and the movable body can be operated at a high speed. It is further an object of the present invention to provide an optical instrument including the movable-body apparatus, and a method of fabricating the movable-body apparatus.
The present invention is generally directed to a movable-body apparatus including a first support member, a movable body, an elastic supporting unit having a twisting longitudinal axis, and a driving unit for tilting the movable body in a tilting direction about the twisting longitudinal axis. The elastic supporting unit supports the movable body flexibly and rotatably about the twisting longitudinal axis relative to the first support member. The driving unit includes a stationary portion provided apart from the movable body, and a moving core formed of a magnetic material, provided on a portion of the movable body, and has a face opposed to the stationary portion.
More specifically, the following constructions can be preferably adopted based on the above fundamental construction.
The stationary portion of the driving unit typically includes a stationary core formed of a soft magnetic material and a coil wound on the stationary core. Further, the elastic supporting unit includes a pair of torsion springs disposed along the twisting longitudinal axis opposingly with the movable body being interposed.
The moving core and the stationary core can have faces opposed to each other in an approximately parallel relationship with a spacing being interposed between the opposed faces of the moving core and the stationary core, respectively, the faces can be shifted from each other in a direction perpendicular to the tilting direction, and the faces can be arranged such that a superimposing area between the faces viewed from a direction perpendicular to the faces can be changed as the movable body is tilted. Thus, there can be achieved an electromagnetic actuator in which a magnetic force can be generated in a direction perpendicular to the support member. When the thickness of the moving core in the tilting direction is appropriately set, a large magnetic force can be generated over a large stroke. Further, since no electric wiring is formed on the movable body, the possibility of disconnection of the electric wiring is greatly decreased, leading to a prolonged life of the apparatus. The moving core and the stationary core can readily constitute a serial magnetic circuit through the spacing.
The moving core can be formed of either a soft magnetic material or a permanent magnet of a hard magnetic material. When the moving core is formed of a soft magnetic material, the driving principle is as follows. Magnetic poles of the soft magnetic material are not determined, and the soft magnetic material is attracted into a magnetic flux generated by the stationary core, such that a cross-sectional area where the soft magnetic material crosses the magnetic flux increases. The movable body is thus driven. Upon cease of the magnetic flux, the soft magnetic material is released from the magnetic flux.
When the moving core is formed of a hard magnetic material, the driving principle is as follows. Magnetic poles of the hard magnetic material are determined, and the soft magnetic material is driven by an attractive force between different magnetic poles or a repulsive force between common magnetic poles. When the moving core is formed of a greatly magnetized hard magnetic material having a large coercive force, the magnetic force can be increased by not increasing the turn coil of the coil and a current applied to the coil. A compact movable-body apparatus with a small consumption electric power, such as an electrostatic actuator, can be obtained.
The moving core can be provided on a side of a side surface of the movable body parallel to and remote from the twisting longitudinal axis. The moving core can also be provided on the side surface itself. In such an arrangement, the freedom in location of the driving unit can be increased, and a magnetic circuit with a small leakage of the magnetic flux can be constructed. Hence, the consumption electric power can be reduced, and the energy efficiency can be increased. Further, a magnetic force perpendicular to the support member can be readily generated, so that the tilting stroke of the movable body can be increased.
The stationary core can have opposite end faces with the moving core being interposed between the opposite end faces. In such a structure, a leakage of the magnetic flux can be reduced, and the magnetic force can be effectively generated. Further, since the magnetic force is determined by a permeance of the spacing between the stationary core and the moving core, a large magnetic force can be effectively generated in such a structure in which a longitudinal side of the moving core can all be used as the width of the magnetic path.
The stationary core can have opposite end faces lying on a common plane and opposed to the face of the moving core. In such a structure, a structure with no fear that the movable body interferes with the stationary core can be readily constructed, and an optical deflector with a large deflection angle can be readily attained.
The moving core can be provided on an edge port ion of the movable body extending parallel to the twisting longitudinal axis. In such a structure, the moving core can be located at a portion of the maximum moment arm, and hence, an effective torsional oscillation can be achieved.
The moving core can be provided on an edge portion of the movable body extending perpendicularly to the twisting longitudinal axis. In such a structure, the opposed faces of the moving core and the stationary core can be readily caused to interfere with each other irrespective of the configuration of the stationary core, and hence, an optical deflector with a large deflection angle can be readily achieved.
The moving core can be provided on a protruding portion of the movable body extending perpendicularly to the twisting longitudinal axis. In such a structure, the moment arm can be further increased, and a large torque can be generated.
In the above three structures, the moving core is arranged close to the stationary core in the magnetic circuit. Therefore, undesired magnetic forces in directions other than the tilting direction of the movable body are unlikely to occur. In contrast, where a moving core is also formed in a portion on a side opposite to the side of the stationary core about the twisting longitudinal axis (typically where a moving core is formed over all of the movable body), the magnetic force from the stationary also acts on the portion of the moving core on the opposite side of the stationary core. Accordingly, a torque in a direction opposite to a direction of a torque generated between the stationary core and a portion of the moving core on the side of the stationary core undesirably occurs. Thus, in those structures, the generated magnetic force can be effectively employed to drive the movable body.
Further, when the movable body is driven in a vibratory fashion, the moving core is subjected to alternate magnetization by the stationary core, and hence, hysteresis loss and eddy current loss (so-called iron loss) are generated. Those losses undesirably lower the efficiency of the apparatus. In a structure in which the moving core is provided solely at a location close to the stationary core, those losses can be greatly reduced, so that apparatuses with a high efficiency and a small consumption electric power can be readily achieved.
Furthermore, those losses result in heat generation in the moving core and the movable body, which causes thermal deformation thereof. Particularly, where the moving core is formed over all of the movable body, a larger deforming stress is generated in the movable body due to a difference in the coefficient of thermal expansion between the moving core and thew movable body. In contrast thereto, in the structure of the present invention, since the moving core is provided on a portion of the movable body, heat generation is unlikely to occur. Further, deformation of the movable body due to the heat generation can be reduced since the interface area between the moving core and the stationary core having different coefficients of thermal expansion is decreased. Moreover, the moment of inertia of the movable body can be decreased, so that the movable body can be readily driven at a high rate.
The moving core can be provided on each edge portion of the movable body about the twisting longitudinal axis, and the stationary core with the coil wound thereon can be provided on each side of the twisting longitudinal axis. Thus, the moving core and the stationary core constitutes a serial magnetic circuit on each side of the twisting longitudinal axis. In this case, a couple of forces in the tilting directions of the movable body can be generated by using attractive and repulsive forces occurring between the moving cores and appropriately magnetized stationary cores. Accordingly, the torque can be simultaneously applied to both end portions of the movable body, respectively, and hence, the driving force can be increased. Further, a structure, in which a displacement in directions other than the tilting direction is unlikely to occur, can be obtained. In addition, even when the movable body is driven at a frequency other than the resonance frequency by alternately energizing the coils, the light deflection can be efficiently performed without decreasing a scanning angle.
When a pair of stationary cores are provided at a location of the moving core provided on each edge portion of the movable body, each stationary core can share the driving function in each one direction of a two-dimensional driving of the movable body.
The moving core can be provided on one edge portion of the movable body, and the stationary core with the coil wound thereon can be provided on one side of the twisting longitudinal axis. In this structure, the moment of inertia required to drive the movable body can be reduced. Further, the size of the entire apparatus can be reduced since the area occupied by the stationary core with the coil can be decreased.
The elastic supporting means can be composed of two sets of paired springs which are capable of torsional and flexure vibrations, whose longitudinal axes are orthogonal to each other and which elastically support the movable body in a two-dimensional torsional manner, and four moving cores can be provided on the movable body in a crisscross pattern extending in directions shifted by 45 degrees from each adjacent longitudinal axis of the paired springs. Further, four stationary cores with the coils can be provided such that each corresponding moving core and stationary core constitute a serial magnetic circuit. In such a structure, the movable body can be tilted in a two-dimensional manner by selectively energizing the four coils.
The movable-body apparatus can further include a second support member for supporting the stationary core, and a spacer support member for bonding the first support member and the second support member to each other in a predetermined relationship with the spacer support member being interposed. In such a structure, the movable body, the elastic supporting unit, and the moving core can be integrally formed in the first support member by using semiconductor producing technique, and the coil and the stationary core can also be integrally formed in the second support member by using semiconductor producing technique. And, those support members can be assembled by using the spacer substrate with appropriate alignment mechanisms. Accordingly, a narrow spacing between the moving core and the stationary core can be precisely set, so that the apparatus can be made compact and the magnetic force for driving the movable body can be increased.
At least one of the elastic supporting means and the movable body can be formed of a single crystal silicon. In such a structure, its internal loss can be reduced, and a high energy efficiency can be attained. Further, a structure with a large mechanical Q-value can be achieved when the resonance driving is employed. The single crystal silicon is readily available, and excellent in mechanical characteristics (i.e., physical strength and durability are great, life is long, and specific gravity is small).
The moving core can be formed of a ferromagnetic material. In such a structure, the movable body can be driven with good controllability. Further, the moving core can be formed of a hard magnetic material. In such a structure, an energy efficiency can be increased.
The moving core can also be formed of an alloy including iron and nickel. In such a structure, the core can be composed of a magnetic material having a large saturation magnetization, a small residual magnetization, and a small loss. Accordingly, an ideal magnetic circuit can be constructed, and an energy efficiency can be increased.
The moving core, the elastic supporting means, and the first support member can be integrally formed in a common substrate. In such a structure, no assemblage process is needed, and the fabrication cost can be reduced. Further, no alignment between the movable body and the support member in needed.
The stationary portion of the driving means typically includes a stationary core fixed to the first support member, and a coil wound on the stationary core. In such a structure, the movable body can be controlled by changing a current flowing through the coil.
Each of the stationary core and the moving core can include a comb-shaped portion, and the comb-shaped portions of the stationary core and the moving core can be arranged in a meshing manner with spacing being interposed between the comb-shaped portions. In such a structure, the magnetic force for driving the movable body does not decrease inversely proportional to the square of the spacing gap, and can be determined by the current flow in the coil, so that the movable body can be readily control led. Further, the maximum area of opposed faces between the moving core and the stationary core can be increased, and hence, the magnetic force can be enlarged.
The frame member can include an inner frame member and an outer frame member, the movable body can include an inner movable body and an outer movable body which is the inner frame member for supporting the inner movable body through a first elastic supporting unit and is supported by the outer frame member through a second elastic supporting unit. In this structure, the inner movable body is supported flexibly and rotatably about a first twisting longitudinal axis of the first elastic supporting unit, and the outer movable body is supported flexibly and rotatably about a second twisting longitudinal axis of the elastic supporting means. If necessary, more than two movable bodies can be flexibly and rotatably supported in such a manner (i.e., in a so-called gimbals fashion). The twisting longitudinal axes typically extend forming an angle of 90 degrees.
The movable-body apparatus can further include a light deflecting element provided on the movable body, and the movable-body apparatus can thus be constructed as an optical deflector. The light deflecting element can be a light reflective surface, a diffraction grating, or a lens. When the reflective surface is used, the apparatus can be readily fabricated, and the movable body can be lightened. When the diffraction grating is used, an incident light beam can be deflected as a plurality of beams. When the lens is used, the deflection angle can be increased.
The movable-body apparatus can be constructed as an actuator for actuating the movable body, or a mechanical-amount sensor with a sensing unit for detecting a relative displacement between the support member and the movable body. A conventional sensor can be used as the sensing unit.
The present invention is also directed to a movable-body apparatus which includes a support member; a movable body; an elastic supporting unit which has a twisting longitudinal axis, and supports the movable body flexibly and rotatably about the twisting longitudinal axis relative to the support member; and a driving unit for tilting the movable body in a tilting direction about the twisting longitudinal axis, which includes a stationary core formed of a soft magnetic material with a coil wound on the stationary core and provided apart from the movable body, and a moving core formed of a magnetic material and provided on a portion of the movable body. The moving core and the stationary core have faces opposed to each other in an approximately parallel relationship with a spacing being interposed between the opposed faces of the moving core and the stationary core, respectively, the faces are shifted from each other in a direction perpendicular to the tilting direction, and the faces are arranged such that a superimposing area between the faces viewed from a direction perpendicular to the faces can be changed as the movable body is tilted.
The present invention is also directed to a movable-body apparatus which includes a support member; a movable body; an elastic supporting unit which has a twisting longitudinal axis, and supports the movable body flexibly and rotatably about the twisting longitudinal axis relative to the support member; and a driving unit for tilting the movable about the twisting longitudinal axis, which includes a stationary core formed of a soft magnetic material with a coil wound on the stationary core and provided apart from the movable body, and a moving core formed of a magnetic material and provided on a side of a side surface of the movable body.
The present invention is also directed to a scanning type display which includes the above-discussed optical deflector, a modulatable light source, a control unit for controlling modulation of the modulatable light source and operation of the movable body of the optical deflector in an interlocking manner, and a display screen on which the beam of light from the deflector is projected. The size and cost of such a display apparatus can be reduced.
The present invention is also directed to an image forming apparatus which includes the above-discussed optical deflector, a modulatable light source, a control unit for controlling modulation of the modulatable light source and operation of the movable body of the optical deflector in an interlocking manner, and an image forming surface on which the beam of light from the deflector is projected. The size and cost of such an image forming apparatus can be reduced.
The present invention is also directed to a method of fabricating the above movable-body apparatus, which includes a step of forming the light deflecting unit on a substrate, a step of forming the moving core on the substrate, and a step of simultaneously forming the elastic supporting unit, the movable body and the first support member in the substrate. The method can further include a step of forming a groove for alignment on the substrate by etching. In such a method, the light deflecting unit is formed in the groove of the first support member formed by the etching process, and after the moving core is formed on the first support member, the elastic supporting unit and the movable body are simultaneously formed. The apparatus can be precisely fabricated by such a method using micromachining techniques.
The above method can further include a step of fabricating a second support member provided with the stationary portion of the driving unit and a groove for alignment, a step of fabricating a spacer support member provided with grooves for alignment on both surfaces thereof, and a step of bonding the first support member to the second support member with the spacer support member being interposed while establishing alignments of the alignment grooves on the first support member and the second support member with the corresponding alignment grooves on the spacer support member through fibers in the alignment grooves.
The step of forming the moving core on the substrate can include a step of forming an electrode for electroplating on the substrate, a step of forming a photosensitive layer on the substrate with the electrode for electroplating, a step of partially exposing the photosensitive layer by using high-energy radiation light, a step of developing and removing a predetermined portion of the photosensitive layer by utilizing a difference in an etching rate between exposed and unexposed portions of the photosensitive layer, and a step of electroplating metal in the removed predetermined portion. The moving core can be precisely formed at a desired location by such a method.
Light at a wavelength less than 400 nm is preferably used as the high-energy radiation light. When the high-energy radiation light is ultraviolet radiation at a wavelength less than 400 nm which is used in an ordinary photolithography, the method is preferable in fabrication time and cost required for photolithography apparatus and process. In this case, when SU-8 (product of MicroChem Corp.) or the like is used as a photosensitive material, a die having a thickness of about several hundred micrometers can be formed.
In the step of simultaneously forming the elastic supporting-unit, the movable body and the first support member in the substrate, they can be formed in the substrate by etching. A smooth structure of a single crystal silicon can be formed by such a method, and an apparatus having ideal processed surfaces can be obtained.
In the step of simultaneously forming the elastic supporting-unit, the movable body and the first support member in the substrate by etching, the substrate can be etched only from its surface without the moving core formed thereon. The apparatus can be formed without damaging the moving core formed in the previous step.
The present invention is also directed to a method of fabricating the above movable-body apparatus which includes a step of forming a groove in a substrate, a step of forming the moving core in the groove, and a step of forming the elastic supporting unit and the movable body in a portion of the substrate such that the support member is formed in the other portion of the substrate. In such a method, the elastic supporting unit and the movable body can be simultaneously formed, and no alignment between the elastic supporting unit and the support member is needed. Further, no assemblage process is needed, and the fabrication cost can be reduced.
The elastic supporting unit and the movable body can be formed by reactive ion etching. The elastic supporting unit and the movable body can be stably formed with high precision by this method.
The elastic supporting unit and the movable body can be formed by etching using an alkaline solution. The elastic supporting unit and the movable body can be stably formed with high precision by an anisotropic etching method utilizing a difference in the etching rate of silicon crystal faces. Further, since the etching rate of this etching method is faster than that of the reactive ion etching, processing time and cost can be reduced.
The moving core can be formed by electroplating. The moving core can be speedily and thickly formed, compared with vacuum-evaporation and sputtering.
These advantages, as well as others will be more readily understood in connection with the following detailed description of the preferred embodiments of the invention in connection with the drawings.